use server admin email for certbot

tasks/install.yml

@@ -3,7 +3,7 @@
   ansible.builtin.include_role:
     name: air.apache
   vars:
-    cert_bot_email: "{{ piwigo_admin_email }}"
+    cert_bot_email: "{{ piwigo_server_admin }}"
     cert_bot_domain: "{{ piwigo_server_name }}"
 
 - name: Install MariaDB